In order to fix an internal-portion rotation body of a damper comprising the internal-portion rotation body and an external-portion rotation body to an attachment-support member turnably supporting a handle, there is a structure provided with a boss on one of both end portions of the internal-portion rotation body, and a rib on the other of both-end portions of the internal-portion rotation body. (See Patent Document 1) The external-portion rotation body is fixed to the handle. The damper is fitted between a pair of legs of the support member. In one of a pair of legs, there is formed a slot relative to the aforementioned rib, and in the other of a pair of legs, there is formed an attachment hole relative to the aforementioned boss. The internal-portion rotation body of the damper is adapted to be fixed to the support member on a side of the rib by sliding and inserting the rib into the slot, and to be supported in the support member on a side of the boss by fitting the boss into the attachment hole. Hence, in a method of the Patent Document 1, when the damper is embedded, there is no choice but to fit the boss into the attachment hole by elastically deforming a pair of leg sides, so that it is difficult to smoothly fit the damper between a pair of legs.